Antenna coupling apparatus



E.'L. MINNICH ANTENNA COUPLING APPARATUS Nov 17, 1959 I Filed Feb. 7, 1956 I INVENVTVOR. EDWARD L.

ATTORNEY.

United States Patent 2,913,725 ANTENNA COUPLING APPARATUS Edward L. Minnich, Carlisle, Pa., assignor, by mesne assignments, to Dynamics Corporation of America, New York, N.Y., a corporation of New York Application February 7, 19 6, Serial'No.'563,972 4 Claims. (Cl. 343-851) This invention is a continuation-in-part of my copending application SerialNo. 483,948,filed January 25, 1955,

, and relates to simplified antenna cou'plingarrangements which can be used to advantage for coupling the output power of a transmitter to the antenna used to radiate the transmitted signal, for signal reception from an antenna and are well suited for transmission and reception using the same antenna in accordance with well'known duplexing arrangements.

With the radio communications traflic of all the allocated service bands steadily increasing, the problem of interference between the various transmissions becomes more acute. As the available spectrum is fixed and the allocations of bands within fixed limits has been made on a quasi-permanent basis by the FCC, the only alternative which can be resorted to when additional interference cannot be tolerated is the imposition of more stringent requirements for each transmission in a particular band. These limitations require that spurious radiations from the radio equipment be reduced to a very low'level. In particular, in private radiotelephone service such as, for example, the marine radio telephone band, the reduction of harmonic radiations to a greater degree than heretofore attained is desirable.

In accordance with the present invention it has been found that improved transmission and reception characteristics can be achieved by means of an antenna coupling circuit in which an elongated coil such as a helix is disposed in axial alignment with a flat coil such as a. multiple turn spiral preferably at the low potential end of the helix. With this arrangement good electromagnetic coupling between the coils is achieved while the efiective mutual capacitance is reduced to a low value.

It is the principal object of the present invention to provide in radio communication apparatus improved and simplified antenna coupling arrangements.

Another object is to provide antenna coupling arrangements having extended attenuation of harmonic frequencies.

A further object is to provide improved antenna coupling arrangements which provide convenient adjustment for obtaining optimum performance under all conditions of operation.

Another object is to provide the foregoing coupling arrangements which are simple and economical in construction and completely reliable in operation while achieving the extended performance characteristics heretofore described.

Another object is to provide an antenna coupling system of minimum capacitance coupling configuration while facilitating making selective tapped or continuous connection to one of the inductive members.

These and other objects are obtained in the present invention by coupling between the tuned circuit of the radio apparatus and the antenna with a spiral coil coupled to a helical coil. A sliding contact or progressive taps on the spiral coupling coil facilitate making a variable con- 2,913,725 Patented Nov. 17, 1959 "ice nection to any portion of all turns of the spiral coil without excessive lead length or other disadvantage due to the requirement for variable coupling connections. Switch tap connections to an antenna loading coil are provided for difierent operating conditions.

In the drawings:

Fig. 1 is a partially schematic view of an antenna coupling system showing a side elevation of the coupled coils of the system;

Fig. 2 is a front elevation of the spiral coil according to the invention; and

Fig. 3 is a sectional view of a modification adapted for continuous adjustment.

Referring to Fig. 1 the'system is shown having a conventional antenna 4 for the transmission or reception or both of radio signals and may be connected to a loading coil 5. The loading coil 5 has connections at a series of taps 6-6 which are individually selected by a switch contact 7 for connection with either of two leads 8 and 9. The leads 8 and 9, respectively, terminate in spring clip connectors 10 and 11.

The antenna 4 transduces energy for a radio circuit 14 which has associated therewith a parallel resonant circuit in which the inductance includes a helical coil 15. The radio circuit 14 may be a transmitter, a receiver or any of the transceiver arrangements for which the antenna 4 will function to transmit or receive energy as required. As an important application of'the present invention relates to transmitters, the subsequent description will be made for the circuit 14 as a radio transmitter with the coil 15 being the resonant inductance in the power output circuit thereof.

The coil 15 is connected in circuit by capacitor 16 and is directly grounded at the opposite end to a chassis terminal 17. "The-terminal 17 may be integrally formed with a metallic chassis 18 which also serves as support and shield for the coil 15.

Mounted to the chassis 18 is an assembly comprising separate plates 19 and 20 of insulating material which may be secured together by any suitable means. The plate 19 is adjacent the grounded end of the coil 15. On either face of the plate 19 is supported a spiral coil 23 which may be imbedded in the surface of plate 19 but out of contact with the coil 15. Instead of the spiral coil 23, a series of connected concentric circles may be employed which will be considered a special form of spiral but in either case the various convolutions thereof lie in the same plane in close proximity to the helix coil 15. Variable coupling is obtained by variation of the spacing between the base of helical coil 15 and the plane of the spiral coil 23.

The coil is provided with a series of taps which may be formed as loops 24 projected at right angles to the plane of the coil 23. The loops 24 project through appropriately spaced holes in the plate 20. One end of the spiral coil 23 is connected to ground at the lug 17. The spring clip connectors 10 and 11 are arranged for connection to selected ones of the projecting loops 24.

In Fig. 2 the spiral coil 23 is shown as it appears behind plates 19 and 20 of transparent insulating material. Projecting through the plate 20 are the loops 24 with one or more loop taps being provided in each turn of the spiral 23. The radial position of the loops or taps 24 with respect to the center of the spiral progresses for each turn with the result that taps on adjacent turns are radially spaced by a fraction of a turn to facilitate making con nections thereto.

In Fig. 3 an alternative selective connection to the turns of the spiral coil 23 is provided to effect a continuous adjustment. The coil 23 is secured to the supporting plate 19 on the surface remote from the base of helix 15. In

1 tion.

this accessible position a sliding connector 31 is placed in contact with a turn of the coil 23. The contact 31 is shownas a single C-shaped spring clip which can be manually moved in sliding engagement with the convolutions of the coil 23 for continuous adjustment. Any other form of rolling or sliding contact suitable for the purpose can be employed and may be desirable especially for printed circuit constructions.

It is to be understood that printed circuits or etched plate techniques lend themselves admirably to this inven- In applications where the level of power to be handled in the spiral coil is low, printed circuitry techniques can be employed with the-set of tap connections 24 riveted, soldered, or otherwise, suitably attached thereto. 1

The operation of the present invention as used in a radio telephone transmitter, for example, the marine radio band has resulted in highly satisfactory performance together with an improvement of approximately db attenuation of second harmonic radiation. Operation in the upper half of the band is effected with switch 7 in position to connect lead 8 to one of the sets of taps 6 on loading coil 5. Insimilar manner operation on the lower half of the band obtains with switch 7 connecting loading coil sets of taps 6 to lead 9. Coupling adjustments in the difierent band switch positions are made by means of respective clips 10 and 11.

Many variations of the disclosed embodiments will be apparent to those skilledin the art in the light of the present teaching and are to be considered Within the scope of the invention as defined in the appended claims.

I claim:

' l. A radio transmitting coupling system comprising a radiating antenna, a loading coil for said antenna having a plurality of sets of tap connections, separate leads for connection to respective sets, switch means for selectively connecting one of said leads to one of said sets of taps, said switch means further selectively connecting one of the taps of each set to the selected lead, a transmitter tuned power output circuit including a helical coil having one end grounded, a flat spiral coil having a plurality of turns with tap connections to individual ones of said turns, means for mounting said spiral coil with the plane of said spiral perpendicular to the axis of said helical coil at said grounded end and substantially centered on said axis, a ground connection for said spiral coil, and means for selectively connecting said leads to individual taps on said spiral coil.

2. Apparatus according to claim 1 in which said spiral coil is formed parallel to the surface of a flat dielectric sheet having holes therein with said holes in registry with said taps and said tap connections projecting through said holes.

3. A radio signal coupling system comprising an antenna, a loading coil for said antenna, a tuned circuit having a helical coil, a flat spiral coil one end of which is at radio fiequency ground potential having a plurality of turns with tap connections to individual ones of said turns, means for mounting said spiral coil with the plane of said spiral perpendicular to the axis of said helical coil and centered on the axis thereof at said'grounded end, and circuit means for selectively connecting said antenna to said tap connections.

4. In an antenna circuit, an elongated coil one end of which is at radio frequency ground potential, a flat References Cited in the file of this patent UNITED STATES PATENTS 1,837,678 Ryder Dec. 22, 1931 1,880,198 Gebhard Oct. 4, 1932 2,541,810 Columbe Feb. 13, 1951 2,560,558 Davis July 17, 1951 FOREIGN PATENTS 333,150 Great Britain Aug. 5, 1950 

